The function of a capacitor

Release Date:

2023-02-22

In a DC circuit, a capacitor behaves as an open circuit. A capacitor is a component that can store electric charge and is one of the most commonly used electronic components.

　　In a DC circuit, a capacitor is equivalent to an open circuit. A capacitor is a component that can store electric charge and is one of the most commonly used electronic components.

　　To understand this, we need to start with the structure of a capacitor. A simple capacitor consists of two electrode plates at its ends and an insulating dielectric material in between (which may include air). When voltage is applied, the plates become charged, creating a potential difference; however, because of the insulating material in the middle, the entire capacitor remains non-conductive. That said, this behavior holds only as long as the applied voltage does not exceed the capacitor’s critical breakdown voltage. As we know, all materials are, to some extent, insulators; but when the voltage across a material increases beyond a certain threshold, the material can conduct electricity. This threshold voltage is called the breakdown voltage. Capacitors are no exception: once a capacitor is subjected to a voltage exceeding its breakdown voltage, it ceases to function as an insulator. In high-school physics, though, such voltages are rarely encountered in typical circuits, so capacitors generally operate below their breakdown voltages and can be treated as ideal insulators.

　　However, in an AC circuit, the direction of the current varies as a function of time. Since the charging and discharging of a capacitor takes place over a finite period, a time-varying electric field is established between the capacitor plates, and this electric field itself is also a function of time. In effect, the electric current “flows” through the capacitor in the form of an electric field.

Latest News